1. Field of Invention
The present invention relates to a drill press with a switched reluctance motor, and more particularly, to a drill press with a switched reluctance motor having a variable speed and automatic braking for operating a mounted drill bit.
2. Description of the Prior Art
Most prior art drill presses use universal motors and gear or belt reduction drives to power a mounted drill bit. For turning the universal motor on and off in a convenient manner, a switch is utilized. Recent models of prior art drill presses may also employ a brake to shorten the coast downtime of a mounted drill bit. This is accomplished by reconnecting the universal motor into a short circuited generator. This is sometimes referred to as "regenerative" braking or "dynamic" braking. A separate circuit operated by a second contact of the switch engages and disengages the brake. Unfortunately, the optimum brush timing, or "brush lead," is different for a motor and a generator. Thus, braking the motor in the manner described above increases wear and tear on the motor brush and commutator. In addition, the braking action of a universal motor decreases sharply as the motor slows down, increasing the total stopping time.
As will be seen in the discussion that follows, the present invention employs a switched reluctance motor which eliminates the aforementioned problems associated with universal motors, particularly those that employ regenerative or dynamic braking.